Such chip cards are known by the label “dual interface chip cards”. In the contact-type mode of operation, such a chip card behaves like a conventional contact-type chip card, i.e. the power supply and data interchange take place together via contact pads on the surface of the card which are arranged with corresponding mating contacts in a read/write appliance. In the contactless mode of operation, a dual interface chip card behaves like a known contactless chip card, i.e. both the power and the data interchange are provided via an antenna, for example a loop antenna, so that an additional power supply does not need to be provided on the chip card for the purpose of operating the electrical components. In the case of the dual face chip cards, the first and second modes of operation are alternated depending on the read/write appliance with which communication is intended. In the contact-type mode of operation, both the power supply and the data traffic are thus provided via the contact-type interface, whereas in the contactless second mode of operation the power supply and the data interchange are provided via the contactless interface.
One example of use of such a chip card is in mobile telephones, where firstly the card is used as a SIM card and secondly additional functions are implemented via the contactless interface, such as the performance of authentication to an automated teller machine or to a computer system, these appliances having contactless interfaces for communicating with the chip card in the mobile telephone.
A problem in this case is that the range in the second, contactlessly operating mode of operation is limited by virtue of a relatively large amount of power being required for operating the chip card and hence error-free data transmission no longer being ensured when the read/write appliance's field is relatively weak.